1. Field of the Invention
The present invention relates to a positioning mechanism of a resolver of detecting rotational position of a rotor with respect to a stator and an electrically-driven power steering apparatus having the same.
2. Description of the Related Art
A brushless motor for an electrically-driven power steering apparatus includes a rotor having a permanent magnet and a stator having a plurality of coils. The rotor is rotated by alternately changing electric conduction of the coils. The brushless motor is used for a motor unit of the electrically-driven power steering apparatus of a vehicle. For example, a coaxial brushless motor is used for a rack type electrically-driven power steering apparatus, wherein a rack shaft is inserted into a rotation shaft of the rotor and the stator is disposed in a housing (referred to as a motor housing member) side of the motor unit fixed to a chassis. In addition, the brushless motor is provided with a resolver as a position detecting sensor for detecting rotational position of the rotor with respect to the stator so as to determine timing of changing the electrical conduction of the coils.
In a conventional electrically-driven power steering apparatus, the resolver is constructed with a resolver stator attached to a housing member (referred to as a connection housing member) side connected to the motor housing member and a resolver rotor attached to the rotor side. In the assembly processes for the electrically-driven power steering apparatus, where the motor housing member and the connection housing member are relatively rotatably temporarily-fixed to each other, the connection housing member is relatively rotated with respect to the motor housing member, so that position (phase) matching between the resolver stator and the resolver rotor in a relative rotational direction is performed. As a result, phase mismatching (mismatching of attachment position in the relative rotational direction) derived from the assembling of the resolver stator and the resolver rotor can be compensated (refer to Japanese Patent Application Laid-open (JP-A) No. 2007-1364 (Patent Document 1).
Due to a variation in accuracy of parts of each of the components, the electrically-driven power steering apparatus cannot control the angular phase of the resolver to be at a suitable position. For this reason, the motor housing member and the connection housing member are constructed as separate individual members, in a partitioned structure. After the resolver stator is attached to the connection housing member side, the connection housing member is relatively rotated with respect to the motor housing member.
However, if the motor housing member and the connection housing member are constructed as separate individual members, the number of parts is increased, and the number of assembling processes of assembling the two members is increased. As a result, production cost of the electrically-driven power steering apparatus is increased.
In such a structure that the resolver stator is attached to the connection housing member and, after that, the connection housing member is relatively rotated with respect to the motor housing member, there is a need for a separate process of relatively rotating the connection housing member with respect to the motor housing member. In addition, it is difficult to completely remove the phase mismatching derived from the assembling of the resolver stator and the resolver rotor.